Re: [Make-wifi-fast] mesh deployment with ath9k driver changes

[Pete Heist <pete@eventide.io>]

> On Apr 24, 2018, at 4:34 PM, Toke Høiland-Jørgensen <toke@toke.dk> wrote:
> 
> Not sure. You do get HOL blocking while a packet is retried, basically.
> And ath9k will keep trying way after it should have given up (up to 30
> retries per packet). If you combine this with a lot of backoff for each
> transmission (which is also quite likely in a very congested setting),
> and I suppose it might be possible…

So that means everyone else waits while a packet is sent and re-sent to a station with a weak signal, for example? I see how that would wreck the latency pretty quick with the number of stations connected, plus channel contention with another repeater. It may be a much bigger factor than bloat.

The physical situation is that there’s an AP on the roof of one cabin, and it’s surrounded by about 8 occupied cabins, each with 4 kids, at least one of which is probably curled up inside using Instagram or YouTube. Signals and tx bitrates of the stations are below, for interest. What I’ll try to find out is if it’s the activities of one or two devices that affect things the most, as it appears that mean latency can suddenly go down to < 10ms and up to > 200ms because of “something"...

root@Cabin_12:~# iw dev ap0_1 station dump | grep "signal avg"
	signal avg:	-60 [-67, -61] dBm
	signal avg:	-51 [-58, -52] dBm
	signal avg:	-61 [-64, -64] dBm
	signal avg:	-60 [-61, -69] dBm
	signal avg:	-70 [-72, -73] dBm
	signal avg:	-70 [-71, -79] dBm
	signal avg:	-75 [-78, -79] dBm
	signal avg:	-73 [-79, -76] dBm
	signal avg:	-75 [-80, -78] dBm
	signal avg:	-68 [-69, -74] dBm
	signal avg:	-76 [-77, -86] dBm
	signal avg:	-84 [-87, -88] dBm
	signal avg:	-79 [-81, -82] dBm
	signal avg:	-76 [-81, -78] dBm
	signal avg:	-58 [-59, -65] dBm
	signal avg:	-72 [-74, -79] dBm
	signal avg:	-74 [-81, -75] dBm
	signal avg:	-80 [-82, -84] dBm
	signal avg:	-65 [-69, -68] dBm
	signal avg:	-78 [-81, -81] dBm
	signal avg:	-68 [-69, -78] dBm
	signal avg:	-72 [-73, -81] dBm
	signal avg:	-70 [-76, -71] dBm
	signal avg:	-80 [-81, -89] dBm
	signal avg:	-75 [-78, -78] dBm
	signal avg:	-72 [-76, -74] dBm
	signal avg:	-78 [-82, -80] dBm
	signal avg:	-63 [-66, -68] dBm
	signal avg:	-78 [-85, -79] dBm
	signal avg:	-75 [-78, -78] dBm
	signal avg:	-65 [-69, -68] dBm

root@Cabin_12:~# iw dev ap0_1 station dump | grep "tx bitrate"
	tx bitrate:	43.3 MBit/s MCS 4 short GI
	tx bitrate:	58.5 MBit/s MCS 6
	tx bitrate:	57.8 MBit/s MCS 5 short GI
	tx bitrate:	72.2 MBit/s MCS 7 short GI
	tx bitrate:	52.0 MBit/s MCS 5
	tx bitrate:	26.0 MBit/s MCS 3
	tx bitrate:	57.8 MBit/s MCS 5 short GI
	tx bitrate:	52.0 MBit/s MCS 5
	tx bitrate:	39.0 MBit/s MCS 4
	tx bitrate:	39.0 MBit/s MCS 4
	tx bitrate:	19.5 MBit/s MCS 2
	tx bitrate:	39.0 MBit/s MCS 4
	tx bitrate:	19.5 MBit/s MCS 2
	tx bitrate:	28.9 MBit/s MCS 3 short GI
	tx bitrate:	28.9 MBit/s MCS 3 short GI
	tx bitrate:	6.5 MBit/s MCS 0
	tx bitrate:	39.0 MBit/s MCS 4
	tx bitrate:	58.5 MBit/s MCS 6
	tx bitrate:	72.2 MBit/s MCS 7 short GI
	tx bitrate:	26.0 MBit/s MCS 3
	tx bitrate:	39.0 MBit/s MCS 4
	tx bitrate:	43.3 MBit/s MCS 4 short GI
	tx bitrate:	43.3 MBit/s MCS 4 short GI
	tx bitrate:	6.5 MBit/s MCS 0
	tx bitrate:	28.9 MBit/s MCS 3 short GI
	tx bitrate:	1.0 MBit/s
	tx bitrate:	6.5 MBit/s MCS 0
	tx bitrate:	65.0 MBit/s MCS 7
	tx bitrate:	39.0 MBit/s MCS 4
	tx bitrate:	26.0 MBit/s MCS 3
	tx bitrate:	1.0 MBit/s